One of the great difficulties in a country like Greece is that in almost any urban setting you can dig a hole and find "stuff".
I have not been to Greece since the 1970's but I do distinctly recall walking around Athens and noticing that almost every home seemed to be undergoing "home improvements" i.e. a wheel barrow and other items neatly arranged beside the structure and a few piles of dirt visible.
Being young and curious I could not help but doing a wee bit of 'pillaging' myself. On a tour group to Corinth I strolled behind the group being led through various points of interest. While walking I noticed a pebble that looked different. I picked it up and noticed that not only was it made of white marble but quite clearly had a toe nail carved into it ! I dropped it into my pocket. Later while visiting the Corinth museum I saw a statue with 9 toes. The presence of a bored looking guard sitting next to it restrained me from reaching into my pocket ! Greece at the time had a military government and doing so would have been asking for trouble.
The next day we visited the ancient city of Mycenae ! Just inside the lion gate are the huge Bronze Age tombs excavated by 'Henry' Schliemann. While the rest of the group stared down the now empty shafts I looked behind me. The actual slag heaps left by Henry sat there undisturbed. Again I noticed strange looking pebbles. Discreetly I collected a small handful of small pottery shards (with decorations !) and added them to my pocket.
When we left I 'stashed' the treasures in a side pocket of my suitcase. Good thing too !
At the airport security was tight ! Terrorism being a great problem back in the 70's (and 80's .... and 90's ...... and 00's ...... and 10's) I was led into a curtained off area and thoroughly searched !
I arrived back home with my loot which I gave to my older brother. I had not yet developed the collecting bug. Maybe someday I shall return !
And pillage my way across the tourist sites ......